We study the steady-state dynamical behavior of a set of torsion-coupled pendula in the presence of damping, fluctuating thermal torques, and constant applied torque. For small applied torque, the average angular velocity of the pendula at low temperature is associated with the motion of thermalized sine-Gordon solitons and as the torque is increased the velocity response becomes strongly nonlinear. These results can be used to describe nonlinear response in Josephson transmission lines and weakly pinned one-dimentional charge-density-wave condensates.

We propose an iterative nonlinear solution to the general potential scattering porblem in quantum mechanics. It is illustrated by the case of $N_I$ localized scatterers of arbitrary strengths $V_j$ located at arbitrary points $R_j$ in an infinite lattice, for which we obtain the complete set of bound and scattering states. The numberical evaluation is estimated to take $O\left(N_I\right)$ steps as opposed to $O\left({N_I}^3\right)$ steps by conventional matrix inversion.

We have measured the nucleon-number ($A$) dependence of the production cross sections for dihadron states in which each hadron is required to have large transverse momentum. We find that the $A$ dependence varies with the total dihadron transverse momentum in a manner similar to that previously observed for single hadrons.

A search for W ions having an additional charge of $-\frac{1}{3}e$ has been conducted, using a Van de Graaff accelerator as an ultrasensitive mass spectrometer. The study investigated masses varying from 182 to 192 amu. No evidence was found for the existence of such ions to a limit of 1 part in 1×${10}^{12}$ over the mass range covered.

We show that if the light isoscalar pseudoscalr meson ($h$) proposed by Wilczek and by Weinberg exists, it must be seen in the decay $K^{+}\to {\pi }^{+}h$. The theoretical lower bound and the present experiment upper bound differ by approximately an order of magnitude.

It is pointed out that a global U(1) symmetry, that has been introduced in order to preserve the parity and time-reversal invariance of strong interactions despite the effects of instantons, would lead to a neutral pseudoscalar boson, the "axion," with mass roughly of order 100 keV to 1 MeV. Experimental implications are discussed.

Normally forbidden transitions obeying the selection rules $\Delta K=\pm 1, \pm 2, \mathrm{and} \pm 3$ have been observed in OP${\mathrm{F}}_3$ in the ground vibronic state by a new avoided-crossing technique based on the molecular-beam electric-resonance method. It is shown how this technique can be used in suitable symmetric rotors to study the $K$-dependent terms in the rotational Hamiltonian, the effects of centrifugal distortion on the total electric dipole moment, and the nuclear hyperfine effects off-diagnoal in $K$.

Strong electric potential double layers ($\frac{e\varphi }{k{T}_e}\simeq 14$) are produced in a triple plasma device. The upper bound to $\frac{e\varphi }{k{T}_e}$ reported in earlier experiments is not found. The electron beam which results from acceleration by the double layer maintains its identity with little heating until it reaches the end of the device. Results of a computer simulation are presented which are in qualitative agreement with the experiment and which indicate that the stability of the double layer depends on the length of the system.

We derive an approximate solution to the Korteweg-de Vries equation with slowly varying coefficients for a soliton initial condition. Expressions are given for the amplitude, position, and velocity, and it is shown that the soliton experiences an irreversible loss of energy whenever it travels in a slowly varying medium. These results are applied to an ion acoustic soliton in a nonuniform plasma and are confirmed by comparison with the results of numerical integration of the differential equation.

A neutron-scattering study of the structural phase transition in hydrogen-reduced crystals of SrTi${\mathrm{O}}_3$ shows a systematic enhancement of the central-peak intensity with increasing defect concentration. $T_c$ is found to decrease linearly with increasing carrier concentration. The results provide direct experimental evidence for the involvement of a defect mechanism in central-peak formation.

We report direct observation of pulsed third-sound film thickness oscillations in unsaturated superfluid ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ films using a capacitance technique. Simultaneous measurements of accompanying temperature oscillations allow the first study of the relative amplitudes of these oscillations and the results are in reasonable agreement with the theory of Bergman although some discrepancies are noted.

Dynamical calculations of low-energy-electron-diffraction intensity-voltage curves are carried out for the first time for the case of an incommensurate overlayer-substrate system, Xe-Ag(111). A new scheme was developed to take into account that the substrate (or overlayer) has incident upon it electron beams at angles unrelated to those angles into which the substrate (overlayer) itself diffracts beams. Comparing the calculated curves with experiment, a Xe-Ag(111) spacing of 3.55 ± 0.1 Å is determined.

The Langmuir-Blodgett technique was used to deposit manganese stearate in the form of monolayers. Because of the nature of the method, and a variety of supporting experiments, it is concluded that the Mn atoms are arrayed on a single surface, thus forming literally two-dimensional magnetic materials.

The dynamics of Mn impurities in dilute $\mathrm{Cu}\mathrm{Mn}$ (12, 20, and 43 ppm) have been studied in the spin-glass regime, down to $\sim \frac{T_G}{30}$. In an applied field of 275 Oe, the spins freeze gradually although their motions are highly correlated below a well-defined temperature $T_G$, which is the same as that found in static susceptibility measurements. At $T_G$, no anomaly is found on the impurity correlation time ${\tau }_e$, which is field dependent.

We have studied niobium point contacts which are very consistent and reproducible from junction to junction, in both their dc and high-frequency behavior. We find a strong correlation between the sharpness of the gap structure and the ac Josephson effect, and we present the first quantitative measurements of the far-infrared frequency dependence of the Josephson effect above the energy gap. The measured $I-V$ curves are also compared with available theoretical models.

It is shown that cancellations in a consistent calculation strongly reduce the attractive interaction of plasmons in an electron gas and eliminate the possibility of a bound state of two plasmons in a metal. In degenerate semiconductors with a large static dielectric constant, a residual binding of two plasmons may remain.

Low-energy electron-loss spectra reveal that a majority of common metals react with CdS, CdSe, and most other covalent semiconductors. Furthermore, barrier heights of metals on individual compound semiconductors exhibit a sharp transition as a function of heat of reaction, increasing dramatically above an experimentally determined critical heat of reaction.

The electric-field gradient caused by an intersitital positive muon at near-neighbor Cu nuclei is calculated from first principles. The electron density distribution around the ${\mu }^{+}$ is obtained using the self-consistent density-functional formalism and the Bloch enhancement factor is computed from a band-structure model based on the tight-binding scheme. Good agreement with recent experimental result is obtained.

It is rigorously proved that the analog of free energy for the percolation models has a singularity at zero external field as soon as percolation appears. The singularity is an essential one at least for large concentrations. Results on the asymptotic behavior of the cluster-size distribution are also obtained for percolation models and for the Ising model at low temperatures.

A clear, prompt dimuon signal has been observed in a low-statistics streamer-chamber experiment with 16-GeV/c $\pi p$ interactions. The good mass resolution makes it possible to identify the contributions from $\rho$ and $\omega$ decays and $\eta$ and $\omega$ Dalitz decays. An excess of events is observed in the mass region ∼400-600 MeV which is not accounted for by the above-mentioned decays.